1. Field of the Invention
The present invention relates to a technique of selectively providing an electric conductor at a predetermined site, and particularly to: a method for selectively forming an electric conductor, the method capable of selectively providing an electric conductor by using an supercritical fluid inside a site such as a microscopic hole (pore) with a high aspect ratio, a recess, or a trench (groove); and a method for manufacturing a semiconductor device, the method capable of providing a microscopic wire, plug or electrode by using the selectively forming method.
2. Description of the Related Art
In order to manufacture a microelectronics element such as an integrated circuit, it is mandatory to perform a step of compactly filling a metal inside small holes such as a microscopic groove for forming a wire with a high aspect ratio, a pore for forming a plug or a recess for forming an electrode. In general, such a step utilizes a phenomenon that a metal thin film is deposited on a surface of a substrate or an insulation film on which a microscopic opening has been formed, whereby the metal thin film goes into (coats) the inside of a microscopic pore through the microscopic opening. In other words, an embedding (filling up) technique referred to as a so-called damascene process is generally employed for embedding a metal thin film inside a microscopic pore.
However, in the conventional embedding technique, the metal thin film is deposited from above the microscopic pore. Thus, in the case where the metal thin film insufficiently goes into the inside of the microscopic pore, voids are generated in the microscopic pore. Further, in the case where the metal thin film goes into the microscopic pore is extremely small in amount, it may cause disconnection (failure) of embedded wires or the like. In addition, in a general embedding technique, it is sufficient if a metal is filled only inside a microscopic pore, and there is no need for a metal thin film outside the microscopic pore. Thus, after the step of embedding a metal into the microscopic pore has been terminated, there is a need for a step of removing the metal thin films deposited on a substrate or an insulation film in accordance with a CMP technique or the like. In other words, such a general embedding technique is prone to wastefully use a material for forming a film and the number of steps easily increases. Thus, this technique is uneconomical and not efficient. Such a problem can be solved if a technique capable of selectively filling a metal into a microscopic pore is developed. As one of such techniques, there is exemplified a technique referred to as a so-called selective deposition technique. This selective deposition technique is attempted using a CVD technique, for example.
However, the CVD technique generally requires a high process temperature including a film forming temperature and has a high process temperature dependency. In addition, the CVD technique considerably consumes materials or energy. Thus, the CVD technique has a small process margin. In addition, the CVD technique entails a problem that entry of impurities is probe to occur. Further, a so-called metal CVD technique of forming a metal film in accordance with the CVD technique utilizes undercoat dependency, and thus, materials used for a film to be formed and an undercoat layer are limited. In the metal CVD technique, a metal film can be substantially formed only on an electric conductor such as a metal. In particular, in a so-called organic metal CVD technique using a liquid material, the liquid material is generally unstable, and a process margin is smaller.
In addition, a PVD technique is exemplified as a general method for forming a thin film other than the CVD technique. However, the PVD technique entails a problem that a stepped coating property is low in comparison with the CVD technique. Thus, if an attempt is made to embed (fill up) a microscopic hole while a metal thin film is formed in accordance with the PVD technique, there is a high anxiety that an embedding (filling up) failure occurs. As a result, there is a high anxiety that disconnection (failure) of embedded wires or the like occurs. The PVD technique cannot carry out a selective deposition technique because of its principle. Further, the PVD technique and the CVD technique are low in process density, and thus, entail a problem that throughput is slow.
Further, in recent years, a variety of electronic devices including semiconductor devices have been downsized significantly. Concurrently, microelectronics elements such as integrated circuits have been further miniaturized and highly integrated. In the miniaturized integrated circuit, its internal structure such as wires, plugs, and electrodes are more complicated, more three-dimensional, or finer in comparison with conventional ones. In order to efficiently form the thus structured wires, plugs, or electrodes, for example, it is mandatory to develop a technique capable of efficiently forming wires such as so-called vertical nano-wires. In other words, in order to manufacture a further miniaturized integrated circuit, it is mandatory to develop a technique capable of compactly and efficiently filling a metal inside a groove for forming a wire with high fineness and a high aspect ratio and a pore for forming a plug, or alternatively, a recess for forming an electrode.
However, as described previously, the conventional damascene technique or subtraction technique using the CVD technique or the PVD technique is easily complicated in steps and the number of steps is hardly reduced. Thus, productivity is low and production costs are hardly restrained. In addition, embedding property or filling up property is seemingly limited. In other words, in the conventional microscopic pore embedding technique, it is thought very difficult to keep track with further microscopic or highly integrated circuit. In order to solve such problems associated with the conventional microscopic pore embedding technique, there has been recently proposed an embedding technique referred to as a supercritical chemical deposition technique of forming a metal film and selectively embedding a microscopic pore by using a so-called supercritical fluid. This supercritical chemical deposition technique is described in Clean Technology (June 2004, Japan Industrial Publishing Co., Ltd.; pages 55 to 58) or Semiconductor FPD World (August 2004, pp. 44 to 47), for example. However, research and development of this supercritical chemical deposition technique has just started recently, and the technique has not yet reached a practical stage capable of enduring a step of manufacturing an integrated circuit or a semiconductor device as a practical product.